Recent advances in technology, particularly in the area of tactical aircraft, have resulted in aircraft with greatly expanded performance capabilities and have produced a corresponding demand for expanded simulator training capabilities into areas not involved in the past. One of the most important of these areas is low altitude flight, as found in nap-of-the-earth and terrain-following instances.
Highly accurate altitude-measuring instrumentation that has been developed to permit aircraft to operate effectively in these areas, such as radar altimeters, has created new problems in visual and instrument simulation. The present invention is especially concerned with solving one of the problems inherent in visual simulators in such nap-of-the-earth (NOE) instances.
In the simulator field, visual images are often generated using a camera-model board system in which a TV camera views a reduced scale terrain model through an optical probe. Low altitude operation implies close approach distances to the model board surface. Therefore, an effective probe protection device is needed to permit prolonged operation in this area without the risk of probe damage and damage to the model board surface when a trainee makes a mistake. The need for maximum image quanlity is paramount in a low-altitude simulator, to provide the pilot-trainee with cues which are as realistic as possible.
More and more procurement specifications are requiring correlated, highly accurate simulators of altitude-measuring instrumentation. This implies some means of measuring actual distance to the model as the probe is traveling over it in an analog of the vehicle movement path.
In order to appreciate the requirements that constitute an effective nap-of-the-earth (NOE) visual helicopter simulator device, it is necessary to define certain terms. "Nap-of-the-earth" flight is flight as close to the earth's surface as vegetation or obstacles will permit, while following generally the contours of the earth's surface. In FIG. 7, there is shown a pictorial representation of NOE and how it relates with other low altitude flying.
A "model board surface" is a scaled model of the actual terrain over which the vehicle is to move. The overall size of such a model board can be, for example, 65 feet long and 25 feet high, and the scale for the model board typically ranges between 500:1 to about 2500:1.
The optical probe itself is available commercially as a special design that permits effective nap-of-the-earth training in a simulator apparatus. A long snout, part of the probe configuration, permits simulated maneuvering in and out of trees, hills, etc., and minimizes shadows in small confined areas. Due to the closeness of the probe to the model board surface, probe protection is essential to prevent damage by a trainee.